Voltaire

It is unquestionable that certain words and ceremonies will effectively destroy a flock of sheep, if administered with a sufficient portion of arsenic.

Voltaire

 Doubt is not a pleasant condition, but certainty is absurd.

Jorge Luis Borges

 [Quoted in Borges and Me (quote from 1971)]

This is one of the benefits of extreme age. Nothing matters much, and very little matters at all.

[Borges is 71 at the time]

Samuel Butler

 [The Note-Books of Samuel Butler (1912)]

Prayers are to men as dolls are to children.

Alison Bechdel

 [from The Secret to Superhuman Strength, 2021]

Like many gay people of my generation, I would not behave like a teenager until I was in my twenties.

Hannah Arendt

 [ 1974, during an interview with the French writer Roger Errera. https://kottke.org/tag/Hannah%20Arendt ]

The moment we no longer have a free press, anything can happen....  If everybody always lies to you, the consequence is not that you believe the lies, but rather that nobody believes anything any longer.... And a people that no longer can believe anything cannot make up its mind. It is deprived not only of its capacity to act but also of its capacity to think and to judge. And with such a people you can then do what you please.

Cecil Rhodes

[The quote is everywhere, but no citation found]

Remember that you are an Englishman, and have consequently won first prize in the lottery of life.

[This is what I've always felt about being born in the U.S. I especially remember the first time I visited Mexico as a boy, with my father remarking on the differences we were seeing and the accidents of birth.]

Christina Anne Knight

[From her letter in Free Inquiry, June/July 2021, p. 64]

Religion: a metaphysical system constructed on an architectural framework of superstition and myth, that attempts to explain the nature of reality and the relationship of our species to it, which along with a body of ritual, and a static code of ethical formulation, is perpetuated via cultural transmission, for the psycho-physiological alleviation of existential angst and is epistemologically dependent on magical thinking, delusion, and confirmation bias.

Mark Twain

According to SkepDoc Harriet Hall, Mark Twain "believed bad habits were good because they can be discarded to promote recovery from illness." 

["Mark Twain and Alternative Medicine", Skeptic, 26:2, 2021, p. 6]

Twain "argued that his experience was a testimony in favor of maintaining deleterious personal habits so that they might be discarded later as a form of ballast — but only when it becomes absolutely necessary to do so in order to promote recovery from an illness." 

[https://silo.pub/mark-twain-and-medicine.html]

And here's the full quote:

[Temporarily giving up smoking, coffee, alcohol and more had seemed to cure Twain's stubborn lumbago.] It seemed a valuable medical course, and I recommended it to a lady. She had run down and down and down, and had at last reached a point where medicines no longer had any helpful effect upon her. I said I knew I could put her upon her feet in a week. It brightened her up, it filled her with hope, and she said she would do everything I told her to do. So I said she must stop swearing and drinking, and smoking and eating for four days, and then she would be all right again. And it would have happened just so, I know it; but she said she could not stop swearing, and smoking, and drinking, because she had never done those things. So there it was. She had neglected her habits, and hadn’t any. Now that they would have come good, there were none in stock. She had nothing to fall back on. She was a sinking vessel, with no freight in her to throw overboard and lighten ship withal. Why, even one or two little bad habits could have saved her, but she was just a moral pauper. When she could have acquired them she was dissuaded by her parents, who were ignorant people though reared in the best society, and it was too late to begin now. It seemed such a pity; but there was no help for it. These things ought to be attended to while a person is young; otherwise, when age and disease come, there is nothing effectual to fight them with.

["Following the Equator" by Mark Twain]

Timothy Leary

You are only as young as the last time you changed your mind.